Enriched preparations of lysosomes have been isolated from cardiac and hepatic tissue. These organelles demonstrate dramatic changes in lysophospholipids and free fatty acids during the release of hydrolases. Very pure hepatic lysosomes have been shown to swell and fuse under these conditions, suggesting one mechanism of exocytosis of hydrolases. This interrelationship of the endogenous acid-active phospholipases and lipases with the process of swelling and fusion is most intriguing. Biophysical and pharmacological techniques will be applied to this finding to delineate further the mechanism of release of hydrolases and fusion of lysosomes in vitro. A similar process may be operative in neurosynaptic vesicles containing noradrenalin in heart tissue and adrenal medulla. These organelles will also be studied in this manner. The ultimate goal of this research is to relate the changes in membranes of organelles to the altered permeability of ischemic cardiac tissue, and to depletion of catecholamines in heart failure. Lipid- dependent membrane-bound enzymes will also be studied in this model system. Dystrophic cardiac and skeletal fragmented sarcoplasmic reticulum (FSR) have been analyzed for Ca ions uptake and structural lipids. A high cholesterol-phospholipid molar ratio of dystrophic FSR may be due to lysosomes rather than an intrinsic defect in cholesterol metabolism. We are continuing to investigate whether the defect in Ca2 ion accumulating ability is related to lysosomal hydrolysis of the FSR, to disordered lipid composition or to other factors.